You need to understand... the Rebellion was gaining momentum quickly. Or at least it felt that way to everyone sitting at home... but when "It's a trap" was broadcasted it killed any momentum that the so called rebellion had gained.

See those nerd hearders went as strong as they thought they were. The Empire let them be as strong as they were so when they were out down no one would ever plan on questioning the Emperor again.

Then the Death Star blew up... and the rebellion gained that momentum back.

"it is a trap" is now a running joke with the youth. It is also printed on t-shirts